On Mon, 27 Sept 2021 at 16:18, Simon Glass <s...@chromium.org> wrote: > On Mon, 27 Sept 2021 at 02:48, Peter Maydell <peter.mayd...@linaro.org> wrote: > > So what is missing in the QEMU-provided DTB that it needs? > > Quite a lot. Here are some examples: > > U-Boot has limited pre-relocation memory so tries to avoid > binding/probing devices that are not used before relocation: > > https://u-boot.readthedocs.io/en/latest/develop/driver-model/design.html#pre-relocation-support
It's up to u-boot to decide what it wants to touch and what it does not. QEMU tells u-boot what all the available devices are; I don't think we should have extra stuff saying "and if you are u-boot, do something odd". > There is a configuration node (which is likely to change form in > future releases, but will still be there) > > https://github.com/u-boot/u-boot/blob/master/doc/device-tree-bindings/config.txt I think u-boot should be storing this kind of thing somewhere else (e.g. as part of the binary blob that is u-boot itself, or stored in flash or RAM as a separate blob). > Then there are various features which put things in U-Boot's control > dtb, such as verified boot, which adds public keys during signing: > > https://github.com/u-boot/u-boot/blob/master/doc/uImage.FIT/signature.txt#L135 > > More generally, the U-Boot tree has hundreds of files which add > properties for each board, since we try to keep the U-Boot-specific > things out of the Linux tree: > > $ find . -name *u-boot.dtsi |wc -l > 398 If any of this is actual information about the hardware then you should sort out getting the bindings documented officially (which I think is still in the Linux tree), and then QEMU can provide them. > Quite a bit of this is to do with SPL and so far it seems that QEMU > mostly runs U-Boot proper only, although I see that SPL is starting to > creep in too in the U-Boot CI. > > So at present QEMU is not able to support U-Boot fully. My take is that this is u-boot doing weird custom things with the DTB that aren't "describe the hardware". You should be able to boot u-boot by putting those custom DTB extra things in a separate blob and having u-boot combine that with the actual DTB when it starts. -- PMM